Originální popis anglicky:
insque, remque - insert or remove an element in a queue
Návod, kniha: POSIX Programmer's Manual
#include <search.h>
void insque(void *
element, void
*pred);
void remque(void *
element);
The
insque() and
remque() functions shall manipulate queues built
from doubly-linked lists. The queue can be either circular or linear. An
application using
insque() or
remque() shall ensure it defines a
structure in which the first two members of the structure are pointers to the
same type of structure, and any further members are application-specific. The
first member of the structure is a forward pointer to the next entry in the
queue. The second member is a backward pointer to the previous entry in the
queue. If the queue is linear, the queue is terminated with null pointers. The
names of the structure and of the pointer members are not subject to any
special restriction.
The
insque() function shall insert the element pointed to by
element into a queue immediately after the element pointed to by
pred.
The
remque() function shall remove the element pointed to by
element from a queue.
If the queue is to be used as a linear list, invoking
insque(&
element, NULL), where
element is the initial
element of the queue, shall initialize the forward and backward pointers of
element to null pointers.
If the queue is to be used as a circular list, the application shall ensure it
initializes the forward pointer and the backward pointer of the initial
element of the queue to the element's own address.
The
insque() and
remque() functions do not return a value.
No errors are defined.
The following sections are informative.
The following example creates a linear linked list.
#include <search.h>
...
struct myque element1;
struct myque element2;
char *data1 = "DATA1";
char *data2 = "DATA2";
...
element1.data = data1;
element2.data = data2;
insque (&element1, NULL);
insque (&element2, &element1);
The following example creates a circular linked list.
#include <search.h>
...
struct myque element1;
struct myque element2;
char *data1 = "DATA1";
char *data2 = "DATA2";
...
element1.data = data1;
element2.data = data2;
element1.fwd = &element1;
element1.bck = &element1;
insque (&element2, &element1);
The following example removes the element pointed to by
element1.
#include <search.h>
...
struct myque element1;
...
remque (&element1);
The historical implementations of these functions described the arguments as
being of type
struct qelem * rather than as being of type
void *
as defined here. In those implementations,
struct qelem was commonly
defined in
<search.h> as:
struct qelem {
struct qelem *q_forw;
struct qelem *q_back;
};
Applications using these functions, however, were never able to use this
structure directly since it provided no room for the actual data contained in
the elements. Most applications defined structures that contained the two
pointers as the initial elements and also provided space for, or pointers to,
the object's data. Applications that used these functions to update more than
one type of table also had the problem of specifying two or more different
structures with the same name, if they literally used
struct
qelem as specified.
As described here, the implementations were actually expecting a structure type
where the first two members were forward and backward pointers to structures.
With C compilers that didn't provide function prototypes, applications used
structures as specified in the DESCRIPTION above and the compiler did what the
application expected.
If this method had been carried forward with an ISO C standard compiler
and the historical function prototype, most applications would have to be
modified to cast pointers to the structures actually used to be pointers to
struct qelem to avoid compilation warnings. By specifying
void *
as the argument type, applications do not need to change (unless they
specifically referenced
struct qelem and depended on it being defined
in
<search.h>).
None.
None.
The Base Definitions volume of IEEE Std 1003.1-2001,
<search.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
